As a glow plug having the combustion pressure detecting function added to the glow plug for aiding the start of an internal combustion engine, there has been provided a plug having a combustion pressure sensor packaged therein, as disclosed in JP-A-2002-327919 (page 2, FIG. 1).
This glow plug with the combustion pressure detecting function is equipped with: a cylindrical housing; a metallic center pole having held in the housing with one end side being exposed from the housing, and electrically conducted to a heating member; and a combustion pressure sensor for detecting the combustion pressure in terms of the force which is caused to act on a pipe member by the combustion pressure and transmitted through the center pole. Moreover, a housing portion is formed between the inner circumference on the other end side of the housing and the outer circumference of the center pole. In this housing portion, there is so arranged a combustion pressure sensor composed of a piezoelectric element that it is subjected to a compressive stress (or a preload) in the axial direction.